Rocket motor casing



June 7, 1966 E. F. BAEHR 3,254,487

ROCKET MOTOR CASING Original Filed Jan. 4, 1963 2 Sheets-Sheet l INVENTOR EDWARD F. BAEHR 1W9. muir ATTORNEYS June 7, 1966 E. F. BAEHR 3,254,487

ROCKET MOTOR CASING Original Filed Jan. 4, 1963 2 Sheets-Sheet 2 I] U [U] FIG. 6

FIG 7 FIG. 9

INVENTOR EDWARD F. BAEHR ATTORN EYS United States Patent ROCKET MOTOR CASING Edward F. Baehr, Berea, Ohio, assignor to the United States of America as represented by the Administrator of the National Aeronautics and Space Administration Original application Jan. 4, 1963, Ser. No. 249,539. Divided and this application Sept. 30, 1965, Ser. No.

3 Claims. (Cl. 60-35.6) v

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This is a division of application Serial No. 249,539, filed January 4, 1963.

The present invention relates to an improved regeneratively cooled rocket motor casing that comprises a plurality of channels in engagement with one another wherein each channel is tapered to provide a thickness at each cross-section that meets the necessary strength requirements without excessive weight.

This invention is an improvement of the structure shown in the United States Patent No. 2,943,442 relating to a regeneratively cooled rocket motor casing. In the structure of this patent, a plurality of channels are secured together to form a hollow elongated enclosure with the channel ribs extending radially outward to engage binding means encircling the exterior of the enclosure thereby forming a skin which defines with the channels a series of coolant passages. Aspointed out in this patent, it is essential that the wall of such a casing be thin in order to save weight, and this is accomplished by uniformly varying the height of the channel ribs at successive longitudinal stations along the nozzle portion of the casing. While the structure disclosed in this patent has proved to be satisfactory, each channel has a uniform thickness throughout its entire length which results in excessive .wall strength in certain areas.

The present invention provides a minimum thickness at each channel cross-section that is consistent with the local channel span and differential pressure load. This 'is accomplished by utilizing a sheet of stock having a tapered thickness in certain areas, and removing a plurality pattern outlined blanks from this sheet. The blanks are then bent to form channels having webs and ribs of varying thicknesses.

It is, therefore, an object of the present invention to provide an improved rocket motor casing utilizing tapered channels which insure minimum thicknesses at each channel cross-section that meet the strength requirements established by local channel spans and differential pres sure loads.

Another object of the invention is to provide an inexpensive method for producing channels having variations in wall thickness within required tolerances to meet local thickness requirements determined by local load requirements. 7 7

Another object of the invention is to provide a tapered channel in which the taper extends across the rolling direction of the stock so that the longitudinal properties of the channel material can be utilized to withstand the principal stresses in the final use.

Other objects and advantages of the invention will be apparent from the specification which follows and from Patented June 7, 1966 the drawings in which like numerals are used throughout to identify like parts.

In the drawings:

FIG. 1 is an isometric view of a rocket motor casing showing the assembly at that fabrication stage preparatory to forming the outer closure for the coolant passages;

FIGS. 2, 3, 4 and 5 are enlarged sectional views taken along the lines 22, 33, 44 and 55 in FIG. 1 showing the variations in the heights and thicknesses of the channels along the length of the casing;

FIG. 6 is a plan view of a blank used to form one of the channels after it has been removed from a sheet of tapered stock and cut to the required outline;

FIG. 7 is a side elevation view of the blank shown in FIG. 6 showing the portion of the stock having a varying thickness and the portion having a uniform thickness;

FIG. 8 is a side elevation view of a typical channel that is bent from the blank shown in FIGS. 6 and 7 and contoured to the desired profile of a section through the combustion chamber and nozzle of the rocket motor casing shown in FIG. 1; and

FIG. 9 is a plan view of the contoured channel shown in FIG. 8.

Referring now to the drawings, there is shown in FIG. 1 a preferred embodiment of a rocket motor casing 10 fabricated from a plurality of channels 11 formed from a material capable of withstanding the operating temperatures as well as the corrosive action of the propellants. The channels 11 have webs 12 and ribs 13 of varying lengths and thicknesses at the longitudinal stations indicated in FIG. 1 and shown in detail in FIGS. 2 through *5. These channels are joined together by a brazing material -14 interposed between the contiguous ribs 13 of adjacent channels during the fabrication process.

1 In higlrtemperature installations, high strength wire 16 is wrapped about the assembled channels -11 to form 'a non-porous outer skin and is brazed to the ribs 13 at the points of contact therewith. Contoured metal rib .bon may be used instead of the wire'16 to form the outer casing. By this expedient, the channels 11 are readily converted into conduits which form coolant passages 17 .or chemical milling. This tapers the thickness of a portion A of the sheet which extends inwardly from an outer edge 20 to a centrally disposed station 22. The'thickness variation of the tapered portion A is a simple slope for the nozzle contour shown in FIG. 1 which extends across the direction of rolling of the sheet stock so that the longitudinal properties of the material will be utilized to withstand the principle stresses in the rocket motor casmg 10. The thickness is the greatest at the edge 20 and the least at the station 22 which corresponds to the point of tangency 24 between the convergent portion and the throat portion of the nozzle as shown in FIG. 8. For

nozzles having a different configuration, the optimum local thickness would vary according to the stresses.

While the thickness of the tapered portion A is varied, the remainder of thesheet comprising that portion to the right of the station 22 in FIG. 7 which is ultimately adjacent the convergent portion of the nozzle and combustion chamber has its thickness reduced a uniform amount to provide a portion of constant thickness. In a typical rocket motor casing 10 the sheet of stock was uniformly tapered from a thickness of 0.018 inch at the edge 20 to a thickness of 0.004 inch at the station 22 while the thickness of the remainder of the sheet was likewise reduced to 0.004 inch. For a combustion chamber and convergent portion of the nozzle having a different contour the optimum local thickness would vary according to the stresses.

Subsequent to the thickness tapering operation, the sheet of stock is divided into a plurality of blanks 26 having a pattern outline that is determined by the local width and height requirements. Each blank 26 has a region B which extends inwardly from the edge 20 to a centrally disposed area 28 shown in FIG. 6 which corresponds to the area 30 of minimum diameter in the throat of the nozzle as indicated in FIG. 8.

Referring again to FIG. 6, the width of the blank 26 in the region B diminishes from a maximum at the edge 20 to the station 28 while the thickness likewise diminishes as is seen in FIG. 7. The pattern outlined blank 26 further has a region C which extends inwardly from the opposite edge 32 toward the centrally disposed area 28 and terminates at a tangent point 34 which corresponds to the point of tangency between the convergent portion of the nozzle and the cylindrical portion of the combustion chamber. The width of the blank 26 is constant in the region C as is shown in FIG. 6 while the thickness of this region is likewise constant. The width tapers uniformly from the tangent point 34 to the centrally disposed area 28 while the thickness remains constant to the point 22 as previously described. It will be appreciated that other combustion chamber and nozzle contours will require other specific blank outlines and thicknesses to meet local width and height requirements together with local stresses.

Opposed marginal edge portions 36 and 38 shown in FIG. 6 of each blank 26 are bent to form the ribs 13 shown in FIGS. 8 and 9 of each channel 11. This bending also produces a slight curvature in the webs 12 which likewise vary in width as well as thickness as shown in FIGS. 1 through 5. This semi-elliptical curvature of the web 12 accommodates high internal pressures. Also, the resulting ribs 13 have varying heights and thicknesses as illustrated in FIGS. 8 and 9. In the aforementioned typical rocket motor casing, each channel 11 has a width of 0.165 inch at the outermost edge 20 which tapers inwardly to 0.085 inch at its narrowest portion adjacent the centrally disposed area 28 and tapered outwardly to a value of 0.118 inch adjacent the cylindrical portion of the combustion chamber.

Each tapered channel produced by the formed blank is simultaneously contoured to the profile of a vsection through the rocket motor casing 10 as illustrated in FIG. 8. The contoured channels are assembled in abutting relationship to form the nozzle and combustion chamber. The channels 11 are then spotwelded together or similarly joined, and subsequently the brazing material 14 is introduced between the ribs 13 of adjacent channels. Thereupon the channels 11 are brazed into the assembly forming the rocket motor casing 10 shown in FIG. 1. The channel assembly '10 is wire wrapped, and the wire 16 is brazed to the ribs 13 as well as the adjacent turns thereby forming a plurality of longitudinally extending passages for regenerative cooling.

While a preferred embodiment of the invention has been shown and described, it will be apparent that various modifications can be made to the disclosed rocket motor casing and its method of fabrication without departing from the spirit of the invention or the scope of the subjoined claims. For example, it is contemplated that constant 4 thickness channels may be used wherein the desired thickness variation is provided by grinding or chem-milling only the heat transfer surface. Although this is more costly, it provides heavier and stronger channel ribs for brazing to the ribbon wrap 16.

What is claimed is:

1. A rocket motor casing comprising:

a plurality of elongated channel members extending longitudinally and arranged in contiguous annular relation to form a nozzle and a combustion chamber integral therewith,

the Webs of said channel members constituting the inner surface of the wall of said casing, each of said webs tapering in thickness in a direction from the exit of said nozzle toward said combustion chamber,

the ribs of said channel members extending generally radially outward with adjacent ribs secured together to produce a unitary construction, each of said ribs tapering in thickness in a direction from said exit toward said combustion chamber, and

closure means encircling the assembly and adapted to define with said channel members a plurality of longitudinally extending passages for regenerative cooling.

2. A rocket motor casing comprising:

a plurality of longitudinally extending channel members arranged in contiguous annular relation to form a nozzle and a combustion chamber integral therewith, said nozzle having a convergent portion and a divergent portion on opposite ends of a throat portion, each of said channel members having a web constituting a portion of the inner surface of said nozzle and said combustion chamber, and

a pair of radially extending ribs with adjacent ribs secured together to produce a unitary construction, each of said webs being tapered in width and thickness and each of said ribs being tapered in height and thickness from a maximum at the extreme outermost end of said divergent portion to provide a minimum channel thickness at each cross-section that is consistent with the local channel span and differential pressure load, and

closure means encircling said unitary construction and adapted to define with said channel members a plurality of longitudinally extending passages for regenerative cooling.

3. A rocket motor casing comprising:

longitudinally extending channel members forming a combustion chamber integral with a nozzle having a convergent portion connected to a divergent portion by a throat portion,

each of said channel members having a web constituting a segment of the inner surface of said casing and being tapered in thickness from a maximum at the extreme outermost end of said diver-gent portion to a minimum adjacent said throat portion,

each of said channel members having a pair of radially extending ribs tapered in height and thickness from a maximum at the extreme outermost end of said divergent portion to a minimum adjacent said throat portion for engagement with adjacent ribs to form a unitary construction, and

closure means encircling the assembly and adapted to define with said channel members a plurality of pas sages for regenerative cooling.

References Cited by the Examiner UNITED STATES PATENTS 2,943,442 7/1960 Baehr 60--39.66 X 2,976,679 3/1961 Dalgleish 6039.66 X 3,066,702 12/1962 Tumavicus 138-11l MARK NEWMAN, Primary Examiner.

C. R. CROYLE, Assistant Examiner. 

1. A ROCKET MOTOR CASING COMPRISING: A PLURALITY OF ELONGATED CHANNEL MEMBERS EXTENDING LONGITUDINALLY AND ARRANGED IN CONTIGUOUS ANNULAR RELATION TO FORM A NOZZLE AND A COMBUSTION CHAMBER INTEGRAL THEREWITH, THE WEBS OF SAID CHANNEL MEMBERS CONSTITUTING THE INNER SURFACE OF THE WALL OF SAID CASING, EACH OF SAID WEBS TAPERING IN THICKNESS IN A DIRECTION OF THE EXIT OF SAID NOZZLE TOWARD SAID COMBUSTION CHAMBER, THE RIBS OF SAID CHANNEL MEMBERS EXTENDING GENERALLY RADIALLY OUTWARD WITH ADJACAENT RIBS SECURED TOGETHER TO PRODUCE A UNITARY CONSTRUCTION, EACH OF SAID RIBS TAPERING IN THICKNESS IN A DIRECTION FORM SAID EXIT TOWARD SAID COMBUSTION CHAMBER, AND CLOSURE MEANS ENCIRCLING THE ASSEMBLY AND ADAPTED TO DEFINE WITH SAID CHANNEL MEMBERS A PLURALITY OF LON- 